dsh-double: Self-Management, Self-Evolution, and Dual-Brain Plugins for DeepSeek Harness

`dsh-double` is a self-management plugin for DeepSeek Harness (DSH), designed to address the issue of an agent crashing due to errors after modifying its configuration. It enables self-repair and evolution through a dual-brain mechanism and blue-green deployment. Core features include health probing, automatic rollback, standby wake-up, dual-brain communication, and an HTTP API. The plugin supports configuration pre-checks, trial runs, and automatic updates via CLI or API, ensuring the stability of the primary instance while consuming no process resources in standby.